isi cara ya terima ksih

BC=CD=17
AB=AD=a
keliling=BC+CD+AB+AD
54=(2×17)+2a
54-34=2a
20=2a
a=20/2
a=10

OB^2=AB^2-OA^2
OB^2=10^2-6^2
OB^2=100-36
OB^2=64
OB=8

◆BD=2OB
=2×8
=16 cm

OC^2=BC^2-OB^2
OC^2=17^2-8^2
OC^2=289-64
OC^2=225
OC=15

◆AC=OC+OA
=15+6
=21 cm
◆L=1/2×BD×AC
=1/2×16×21
=168 cm^2